The new MFIndexSpace is usually the result an interface movement operation, followed by some form of LevelSet computation. At the end of this, a new MFIndexSpace is created. The current state data needs to be mapped into a new LevelData<MFCellFAB> based on this new MFIndexSpace. The DisjointBoxLayouts from a_source and a_dest are assumed to be identical. Thus, no coarse-fine AMR operations are performed.